In short: mould appears when a bathroom stays damp longer than it can dry. The most common cause is poor ventilation. Surface mould can be removed yourself, but if it keeps coming back or is behind the tiles, the bathroom needs renovating.
Why does mould appear?
- Ventilation doesn't work: the fan is weak, blocked or missing. Damp air stays in the room.
- The door is shut and air doesn't move: there should be a gap under the bathroom door to let fresh air in.
- Cold outside wall: in a house bathroom, moisture collects on a cold wall and feeds mould.
- A leak behind the tiles: old or damaged waterproofing lets water into the wall.
- Old grout and silicone: water and dirt collect in cracked joints.
What can you do yourself?
- After showering, let the fan run for at least half an hour or leave the door open.
- Wipe the shower wall and floor with a squeegee.
- Clean the grout with a mould remover. Wear gloves and air the room.
- Replace old darkened silicone around the shower and bath.
- Check the fan works: hold a sheet of paper against the vent. If it sticks, the fan is pulling air.
When is a renovation needed?
If mould comes back quickly, tiles are loose or sound hollow when tapped, the wall feels damp or there's a stain on your downstairs neighbour's ceiling, the problem is probably behind the tiles. Cleaning the surface won't help then. The old tiles must come off, the wall must dry and new waterproofing must be done.
During the renovation it's worth fitting a new fan too. A good choice is a fan with a humidity sensor that switches on by itself when the room is damp.
Frequently asked questions
Is mould harmful to health?
Mould can cause allergies and breathing problems, especially in children and sensitive people. So it's best not to leave it for long.
Can I just paint over mould?
No. Mould will soon come through the paint again. First you need to find and fix the cause of the damp.
Does a bathroom with a window need a fan?
Yes. In winter the window won't be left open and the moisture stays in the room.
If mould keeps coming back in your bathroom, ask us for a free inspection. We'll find where the damp comes from and suggest a solution. See also our bathroom renovation service.
